KR920004336Y1 - Circuit for eliminating digital audio tunning noise - Google Patents

Abstract

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Description

Noise prevention circuit for band selection of digital tuning radio

The accompanying drawings are circuit diagrams according to the present invention.

* Explanation of symbols for main parts of the drawings

1: Band selector switch 2: Band selector

5, 6, 12, 13, 14, 15, 16: switching transistor

11: FM front end 17: microcomputer

18: low pass filter 19: MW tuning unit

22: SW synchronization unit

The present invention relates to a band selection circuit of a digital tuning radio for selecting a band for each broadcast by using a button-type band selection switch, and in particular, to prevent noise generated when touching a load antenna when receiving a medium wave (MW) broadcast. The present invention relates to a noise prevention circuit in band selection of a digital tuning radio.

In the acoustic equipment employing the digital tuning system, conventionally, the AM tuner antenna and short wave (SW) antenna coil are used in common. There is a problem in that noise is generated by inducing high frequency components induced in the antenna.

Accordingly, an object of the present invention is to provide a noise prevention circuit when selecting a band of a digital tuning radio such that noise is not generated even when the antenna is touched when selecting a medium frequency broadcasting band.

The present invention for achieving this purpose is a band selector for generating a predetermined level of output for selecting FM broadcast, and AM broadcast including SW and MW band by sharing FM and SW reception rod antenna, and MW of AM. MW receiving tuner receiving broadcasts, SW receiving tuner receiving AM broadcasts, and AM RF amplifiers, FM / AM intermediate frequency amplifiers for detecting FM or AM broadcast signals under predetermined control signal control And an anti-noise circuit when selecting a band of a digital tuning radio having an integrated circuit having an integrated FM stereo multiplexer. Select the FM broadcast, and when the FM is selected, the two first transistors for selecting the FM broadcast with the control signal of the integrated circuit low, and the band is selected when the SW band for AM broadcast is selected. Two SW transistors operated by the high-state signal outputted from the SW, SW band selection switching unit when the second transistor is turned on, and SW radio signals received through the load antenna when the second transistor is turned on It is composed of a SW line switching section including a coil, a capacitor, and another transistor to be applied to the receiving tuning section.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit diagram for preventing noise generated when a person touches an antenna when selecting a MW band of a digital tuning radio according to the present invention. In the circuit shown in FIG. 1, the output condition of the band selector 2 is assumed as follows according to the operation of the band select switch 1.

TABLE 1

First, when the band select switch 1 is not pressed, the outputs ₁ and 2 of the band selector ₂ are both low (0 0). However, since the outputs out ₁ and out ₂ do not pass through the diodes 3 and 4, the transistor 5 is turned off, and thus the transistor 6 is also turned off so that the control signal CONT becomes low. In this case, the integrated circuit 7 having an AM RF amplifier, an FM / AM intermediate frequency amplifier, and an FM stereo multiplexer selects FM broadcasting. In this case, the FM broadcast through the load antenna 8 is input to the band pass filter 10 via the coupling capacitor 9 and then filtered and applied to the FM front end 11.

The FM broadcast signal passing through the FM front end 11 is detected by the integrated circuit 7 and then output. On the other hand, if you want to select the MW band, press the selector switch 1 once, the output of the band selector 2 (out ₁ , out ₂ ) is maintained at "1 0".

Therefore, the output of the high state out ₁ turns on the transistor 5 via the diode 3, and the low state bias is applied to the base of the transistor 6 by the turn-on of the transistor 5. 6) is also turned on. As the transistor 6 is turned on, a high phase control signal CONT for selecting AM broadcast is applied to the integrated circuit 7.

However, it is turned on and transistor 6 at any band selector (2) the output (out ₂₎ Since the low state diode (4 ') is because mothayeo not turn on transistor 12 is turned off, transistor 13 is also off in Thus, the transistors 14, 15 and 16 are also turned off. That is, the signal is not input through the rod antenna 8, and under the control of the microcomputer 17 and the low pass filter 18, the AM broadcast selected by the MW tuning unit 19 composed of the MW antenna coil can be received. Will be. Therefore, in this case, even if a person touches the rod antenna 8, the abnormal noise is not induced to the MW tuning unit 19.

In addition, when the SW band is to be selected, when the switch 1 is pressed once more, the outputs (out ₁ and out ₂ ) of the band selector 2 are maintained at “1 1”. The transistor 12 is turned on because a high bias is applied to the base via the diode 4 '.

In this case, of course, the transistors 5 and 6 are turned on to select AM broadcast.

When the transistor 12 is turned on, the transistor 13 is also turned on, so that the transistor 14 is turned on because a high bias is supplied to its base.

As the transistor 14 is turned on, the SW propagation signal received by the load antenna 8 passes through the SW 20 through the coil 20, the capacitor 21 and the transistor 14, which are series resonance circuits for the SW frequency. Is applied.

In addition, as the transistor 13 is turned on, signals through the bias resistors 23 and 24 are applied to the bases of the transistors 15 and 16, respectively, so that the transistors 15 and 16 are turned on so that the user cannot receive SW propagation. Will be.

If the switch 1 is pressed once more, the output (out ₁ , out ₂ ) state of the band selector 2 becomes "0 0" and the reception mode returns to the FM state.

As such, the present invention is characterized in that no abnormal noise is generated even when the load antenna is touched during MW reception in a band selection circuit using a single tact switch in an acoustic device employing a digital tuning system.

Claims (1)

Band selector (2) for generating FM signals and output signals (out ₁ , out ₂ ) of a predetermined level for selecting FM broadcasting and AM broadcasting including SW and MW bands by sharing FM and SW receiving rod antennas (8). And FM or AM broadcasting under the control of the MW receiving tuning unit 19 for receiving the AM broadcast of AM, the SW receiving tuning unit 22 for receiving the SW broadcasting of AM, and a predetermined control signal CONT. In the anti-noise circuit of band selection of a digital tuning radio having an integrated circuit (7) having an AM RF amplifier, an FM / AM intermediate frequency amplifier, and an FM stereo multiplexer for detecting signals: It is turned on by the signals (out ₁ , out ₂ ) output from the band selector 2 to select AM broadcasting by bringing the control signal CONT of the integrated circuit 7 to a high state, and at the time of FM selection, the integrated circuit. Transistors (5) and (6) for selecting FM broadcasting in a state in which the control signal CONT of (7) is low; When the SW band of AM broadcasting is selected, the transistors 12 and 13 and the SW reception tuning unit when the transistor 13 is turned on are turned on by the high state signals out ₁ and out ₂ output from the band selector 2. A SW band selection switching section including transistors 15 and 16 for operating 22; The coil 20, the condenser 21, and the transistor 14 for applying the SW propagation signal received through the load antenna 8 to the SW receiving tuner 22 when the transistor 13 is turned on. SW line switching unit 100 comprising a noise preventing circuit when the band of the digital tuning radio.